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statistics and carbon analysis

deep and extensive rooting also produces a variety of benefi ts economically valuable to the producer, from drought and erosion resistance to nutrient retention, genetic and agronomic attention could be a broadly cost neutral measure. Because a tree not only retains, but extends

its full structure from year to year, orchards provide better and more enduring carbon capture than annual arable crops. Once again, the effect is not a simple one, but analysis of research data suggests that an organic orchard can remove from 2.5 to 5 carbon dioxide equivalent tons per hectare per year. If further research and analysis support this, orchards would come within the politicoeconomic structures of carbon quota trading. Moving away from agriculture, carbon

emission is often linked to heat; Kit Pedlar used to argue that ‘heat is the ultimate pollutant’. Even the computers upon which analyses depend are culprits: the laptop on which I am writing this, and have recently conducted a carbon effi ciency audit for a factory, is pumping out a continuous draft of distinctly warm air. The massively multicored HPC installations that model climates are high level radiators. They are nothing, however, to industrial processes designed to do mechanical work or to produce heating as an end in itself. Combining these to harness waste output from one as product for the other, especially in conjunction with other necessary processes such as waste disposal and recycling, is an obviously appealing ideal. There have been many experiments and implementations, but the dream has yet to see signifi cant large scale integrative adoption. Analysis of research data (see ‘Analysing joined up heating’) suggests that the dream may indeed be worth pursuing, with signifi cant carbon emission reductions among the benefi ts.

geopolitical issue complicates an already complex carbon balance, as does the concomitant issue of agricultural land lost to food production. In such an atmosphere, scrupulous data analysis becomes as vital as it is diffi cult. Georgescu and others argue[6]

from simulation analytics that to

perennial biofuel crops across the central United States would produce transpiration increases and albedo increase leading to cooling of the local region ‘equivalent to a carbon emissions reduction of 78 tonnes of carbon per hectare’. On the other hand, they do warn that ‘a thorough evaluation of costs and benefi ts ... must include potential impacts on the surface energy and water balance’. Dumortier and others, writing from an economic viewpoint after their own analyses, come to the conclusion[7]


Predicted temperature differences (in °C) resulting from a conversion to perennial biofuel agriculture, from Georgescu[11]

et al: (A) 2m temperature

(perennials minus annuals); (B) as (A) but perennial crop representation does not include albedo modifi cation; (C) as (A) but perennial crop representation includes rooting depth of 2m

For energy requirements with a

higher conversion gradient, economies seem unlikely in the near future to wean themselves away from direct combustion of hydrocarbons, but the rise of biofuels brings a new set of debates. In the United States in particular, biofuels have for some years offered the seductive appeal of independence from both foreign supply and nonrenewable resource. That

Analysing joined up heating

Combined heating and power or cooling, heating and power (CHP, CCHP) systems generate electricity and usable heat from one fuel source. Organic Rankine cycles (ORC) generate power from low- temperature heat sources. Hueffed and Mago, in an extensive SAS mediated study[10]

using buildings in

Boulder, Colorado, examined the effi ciency potential of combining these systems: an ORC linked to a CHP or CCHP. Although carbon emission reduction was not the main focus of the study, improved effi ciency is associated with reduced fuel inputs which, in turn, are linked to lower costs in both fi nancial and environmental emission terms.


The study examined economic, energetic, and environmental performance of these combined systems under various operational strategies, compared to each other, to standalone CHP and CCHP systems, and to a reference model. Analysis of the resulting data showed reductions of between 12 per cent and 17 per cent, not only in operational costs and primary energy consumption, but in carbon dioxide emissions too. Some strategies produced greater carbon reductions still (up to 28 per cent), but only at an increase in fi nancial cost that makes them unlikely to be adopted under current conditions.

‘impact of cropland expansion on carbon emissions is extremely sensitive to model assumptions... [and]... it is very diffi cult to narrow the range of reasonable parameter values to tighten the set of results to a level that would allow robust policy conclusions’. No discussion of statistics in relation

to rising atmospheric carbon levels would be complete without mentioning that data analyses and their interpretation are central to debate over anthropogenicity itself. Rival hypotheses generally rest on suggestions that increases are either natural or illusory partial artefacts of natural cycles, which would suggest that similar patterns should be discernable in the past. Recent[8]


of depositions in the ice record identifi ed two objections to the natural explanations for methane, though not for carbon dioxide. There is no sign of similar methane increase in seven interglaciations prior to the Holocene, while methane emissions from north tropical and boreal wetlands (the two largest global sources) have declined during the past 5,000 years. There is, in fact, a whole literature of

archaeometric data analyses around the history of carbon cycle and its relation to human activity, both before and after the mastery of fi re. It’s a very tempting pathway to follow, both intellectually and for the escape which it seems to offer from science as political football. Alas, the escape is illusory; carbon is too fundamental to every issue affecting human activity at any level for it to ever be left alone.

References and Sources For a full list of the references and sources cited in this article, please visit www.scientifi c-computing. com/features/referencesdec11.php

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